Hydrophobic coating compositions, articles coated with said compositions, and processes for manufacturing same

ABSTRACT

Hydrophobic coating compositions are provided as are processes to coat articles with the compositions. Extremely hydrophobic coatings are provided by the compositions. Durable, weatherable and scratch-resistant coatings are provided by compositions comprising a trifluoromethyl-containing component and a hardenable material. Processes are also provided for forming hydrophobic coatings on articles without any substantial loss of fluorocarbon solvent used in the coating composition. Articles are coated on a surface thereof with a hydrophobic coating reactant or reaction product which forms a coating having an exposed surface populated with 30% by area or more terminal trifluoromethyl groups.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation application of U.S.patent application Ser. No. 09/593,847 filed Jun. 14, 2000, which is adivisional application of U.S. patent application Ser. No. 09/220,884filed Dec. 28, 1998, now U.S. Pat. No. 6,156,389, which is acontinuation-in-part of U.S. patent application Ser. No. 08/795,316,filed Feb. 3, 1997, now U.S. Pat. No. 5,853,894, all of which are herebyincorporated herein in their entireties by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to compositions for coatingsurfaces, surfaces coated with compositions, and methods of formingcoated surfaces. More particularly, the present invention relates tohydrophobic coatings for laboratory vessels and other articles. Thepresent invention also relates to processes for forming a hydrophobiccoating on a surface of an article.

BACKGROUND OF THE INVENTION

[0003] Hydrophobic coatings are useful for many applications, forexample, to prevent rain from wetting-out or collecting on a windshield.Another application of hydrophobic coatings is in the field oflaboratory vessels. Laboratory vessels including chambers, microtiterplates, vials, flasks, test tubes, syringes, microcentrifuge tubes,pipette tips, selectively coated microscope slides, coverslips, films,porous substrates and assemblies comprising such devices are often usedto handle, measure, react, incubate, contain, store, restrain, isolateand/or transport very precise and sometimes minute volumes of liquid,often biological samples. When samples are quantitatively analyzed, itcan be of critical importance that precise and representative amounts ofsample are transferred, or else inaccurate results are obtained. Due tothe different affinities of some materials to adhere to the walls of alaboratory vessel, qualitative analyses such as concentrations ofmaterials may also be adversely affected if certain materials in asample selectively adhere to operational surfaces of the vessel walls.

[0004] Unfortunately, materials typically used in the manufacture oflaboratory vessels do not sufficiently repel many biological samplefluids nor do they sufficiently resist the adherence of molecularconstituents of such a sample fluid. The sample fluids often wet thesurface of the vessel causing residual quantities of liquid sample tocling to an operational surface of the vessel when the sample isremoved. In some cases, significant quantitative and/or qualitativeerrors result. It is therefore desirable to provide extremelyhydrophobic coatings for laboratory vessels which will reduce thewetting of the operational surfaces of the vessels and reduce clingingby even the most adherent samples so that virtually no sample remains inthe vessel when poured, ejected or vacuumed therefrom.

[0005] In some laboratory techniques, it is important to restrain,isolate or limit the position of liquid samples to prescribed locationswithin or on a laboratory vessel, while keeping adjacent surfaces of thevessel substantially free of liquid sample. Such techniques can be usedto facilitate chemical and biological reactions, as well as improvingsample recovery. The prescribed locations may (1) have surfaces that arereactive, (2) have a surface that exhibits a specific affinity, (3)optimize the sample volume to area ratio, (4) restrict sample movementduring at least some vessel motion, and (5) have porous surfaces.

[0006] Vessels for handling, measuring, storing and transporting liquidshave previously been rendered less wettable and less adherent to fluidsby application of silicone compounds to the vessel surfaces which comein contact with the fluid. For example, silane monomers and polymershave been added to polyolefins prior to injection molding, resulting inlaboratory vessels with an improved repellency to many sample fluids andtheir constituents. These materials produce surfaces with surfaceenergies potentially as low as 22 ergs per square centimeter. Inpractice, however, silane treated vessels exhibit surface energies thatmeasure 25 to 30 dynes/cm.

[0007] Drawbacks associated with silane treatments include a continuedwetting of the vessel, adherence to the vessel walls by many samples,chemical reactivity with many reagents, and a tendency for the vessel tobecome wettable following the common practice of autoclaving forsterilization. Silicones are known to freely migrate, leading to worriesover sample integrity. Many pipette tips are plugged with porous filtersto prevent sample contamination from the pipettor barrel, yet these freesilicones make the pipette tips slippery and cause the filters to becomeloose or dislodged. Additionally, silicones must typically be added at alevel of 2 percent by weight to be effective, making the costprohibitive for many price sensitive applications.

[0008] Fluorination processes have been used to treat laboratory vesselsand have resulted in vessels having interior surfaces with surfaceenergies approaching 22 dynes/cm. These processes generally involve thefull or partial replacement of superficial hydrogen by fluorine usingchemical processes or the plasma polymerization of fluorine containinggases. U.S. Pat. No. 4,902,529 to Rebhan et al. discloses a plasma torchprocess using CF₄ or SiF₆ to fluorinate the interior of resin articlesand containers in an attempt to eliminate the use of dangerous mixturesof fluorine and inert gases. This method is impractical, however, fortreating the vast quantities of small vessels consumed by industrial,clinical and research establishments. Furthermore, improvements inperformance over silicone processes are only marginal.

[0009] The plasma polymerization of perfluorobutene onto the exteriorsurface of various articles has been reported to produce exteriorsurfaces with up to 24 percent —CF₃ groups, and a high percentage of—CF₂— groups. Resultant surface energies of 22 to 24 dynes/cm areobtained due to the presence of cross-linkages and numerousmonofluorinated carbons. Time-consuming, carefully controlled RF plasmasemploying fluorine-containing monomers have also been used to reduce thewettability and adhesion of laboratory vessels, producing exteriorsurface energies of 12 to 15 dynes/cm and surface populations of up toabout 25% by area CF₃ groups on exterior non-operational surfaces.Interior operational surfaces, however, are still not reduced to below22 dynes/cm. While these methods offer improvements over silicon-basedtreatments, the time, expense and equipment required are not appropriatefor high commercial volume articles that are often for one-time use andrequire very low inherent cost.

[0010] Perfluoroalkyl polymers and carefully prepared monolayer films ofperfluoroalkyl surfactants are widely recognized as having surfaceenergies below 20 dynes/cm. FEP and PFA Teflons®), available fromDuPont's Polymer Products Department, Wilmington, Del., have surfaceenergies of 15 to 16 dynes/cm with —CF₃ populations as high as 25percent. Extruded and fused Teflon® vessels are currently manufacturedfor special applications involving exceptionally harsh reagents but areexpected to have a long service life because of their high material costwhen compared to the cost of glass or polypropylene vessels.

[0011] Fluoroalkyl polymers have been used to produce oleophobic,hydrophobic membrane surfaces that are not wetted by common organicsolvents. Membranes coated with such polymers are disclosed in U.S. Pat.No. 4,954,256 to Degen et al. These membranes have surface energiesranging from about 6 to about 15 dynes/cm but require a manufacturingprocedure which involves soaking a membrane with a solution containingpolymerizable monomers, exposing the solution-wetted membrane to highdoses of ionizing radiation, and then washing the ionized membrane withorganic solvent to remove unreacted monomer. While no attempts are knownto coat laboratory vessels by such a procedure, it is expected thatdifficulties would arise as well as high cost in coating such vesselsbecause of the shear bulk of the polymerizable solution to be irradiatedand problems with fully washing the coated vessel.

[0012] Methods of making disposable, one-time use laboratory vesselssuch as pipette tips can involve a substantial loss of costly solventwhen a coating solution is used to form a hydrophobic coating. A needexists for a process of coating laboratory vessels at a cost of a fewcents per thousand with an insignificant loss of solvent.

[0013] Recent patents may suggest the practice of solvent recovery inthe application of certain branched fluoropolymers, such as Teflon AF,to articles of manufacture. U.S. Pat. No. 5,356,668 to Paton et al. andU.S. Pat. No. 5,006,382 to Squire are incorporated herein in theirentireties by reference. The mere suggestion of such a recoverypractice, however, does not provide a commercially viable method forcoating many low cost, one-time-use articles, such as pipette tips andlaboratory vessels.

[0014] Environmental concerns about pollution by volatile solvents,especially chlorine-containing materials such as perchoroethylene, havemotivated significant improvement in dry cleaning equipment, resultingin significant reductions in solvent losses. Cleaning and coatingequipment used in the semiconductor, plastics, and metal partsindustries have made similar strides. Better seals and welded ductsaccount for some of the upgrades.

[0015] Operation of these machines according to their suggestedprotocols using fluorinated solvents, however, still results in large,expensive losses. For example, the Renzacci Company of Italymanufactures perchloroethylene-based cleaning machines that are widelyrecognized to be among the best in the industry in terms of minimalsolvent loss. But loaded with 60,000 pipette tips in mono-filament meshbags and using Renzacci's standard automated programs, these machinesloose about 5 pounds of FC84 (3M Company, St Paul, Minn.) per cycle.This translates to solvent consumption costs of over one dollar perthousand tips. Higher boiling point fluorocarbon solvents have lowerloss rates, but the solvent expense is about the same due to theirhigher cost per pound.

[0016] The Renzacci standard automated program partially fills acleaning/coating tank of approximately one-half cubic meter with solventat ambient temperature from a solvent reservoir. Articles in the tankare then tumbled in the solvent for several minutes, followed by drain,spin and spin-rinse cycles. With continued tumbling, a heat pump and asupplementary heat source (electric, steam, etc.) heat air blown throughthe tank, while passing air returns from the tank over chilledcondensation coils where solvent vapor is liquified and returned to thereservoir. Water is circulated through the heat pump system to removeexcess heat. However, the temperature in the tank can still rise to over50° C. and the reservoir temperature can rise to more than 30° C. At theend of the process cycle, heating is discontinued and the tank andreservoir are cooled to about 30° C. When the tank door is opened toremove the cleaned/coated articles, a small blower draws air out of thetank through a carbon filter in order to reduce the odor of remainingperchloroethylene solvent.

[0017] Unfortunately, at 30° C. the solvent FC84 has a vapor pressure ofover one fifth atmosphere, and the half cubic meter tank volume containsabout two pounds of solvent as dense vapor (about 14 times that of air),even without agitation. Opening the tank door results in the immediateloss of this material, at a current cost of about $45 (US). Since themachine will handle about 60,000 tips per run, the loss per thousand isabout 50 cents. The carbon recovery filter is at the top of the tank andis of little practical economic value.

[0018] Additional losses accrue during the heat cycle at 50° C. when themachine fittings and seals are challenged by pressures approaching 1.2atmospheres. Furthermore, it is apparent from other studies that lowmolecular weight fluorocarbon solvents, having boiling points between80° and 120° C. are particularly “slippery” in passing through rubberand silicone gaskets and seals. No machines investigated had moreaggressive containment systems for leak-free operation under theseconditions.

[0019] A need exists for a method of coating large numbers of laboratoryvessels which results in a very low loss of solvent at a surprising andsignificant cost savings.

[0020] Described by Dettre and Johnson in 1964 are phenomena related torough hydrophobic surfaces. Dettre and Johnson developed a theoreticalmodel based on experiments with glass beads coated with paraffin or TFEtelomer. For even moderately hydrophobic surfaces (e.g. about 40dynes/cm or less) with high levels of microscopic roughness, where theaverage height of bumps is close to or exceeds their average width, anaqueous liquid, especially one without surfactant activity, in contactwith the surface only wets the top of the bumps, forming what is knownas a “composite” air-liquid-solid interface. For example, water at reston a surface of this kind may exhibit contact angles greater than 160degrees. This unusual property has been practiced and is the basis for avariety of proprietary microscope slide, plate and membrane productsusing coatings sold by Cytonix Corporation, in Beltsville, Md. However,such products are based on Teflon® and the hydrophobic properties ofdifluoromethylene (—CF₂—) groups, which at best exhibit surface energiesof from about 18 to about 20 dynes/cm.

[0021] A need exists for a method of manufacturing a coating whichexhibits, on all or part of an operational surface thereof, interfacialcontact angles to aqueous samples of 120° and above, even as high as160°, and surface energies well below 20 dynes/cm. According to somedesirable applications, a need also exists for vessels having surfaceenergies of below 10 dynes/cm. This need is especially acute butdifficult to achieve for one-time-use vessels costing only a few dollarsper thousand.

[0022] There is also a need for extremely hydrophobic coatings that aredurable, for example, coatings for articles such as windshields,rainshields, and satellite and/or radar dishes, other signal receiversand transmitters, and radomes. A need exists for a composition which canprovide an extremely hydrophobic and durable coating on a surface of anarticle. Problems associated with water film formation on radomes, andproblems of radar desensitization in rain are described, for example, inthe Honeywell Technical Newsletter entitled RADAR DENSENSITIZATION INRAIN, WATER FILMS ON RADOMES, AND HYDROPHOBIC COATINGS, Nov. 2, 1998,re-published by Cytonix Corporation with permission from Honeywell,Inc., said newsletter being incorporated herein in its entirety byreference. A need exists for a coating composition for a signaltransmitter or receiver, wherein the composition can be applied and forman extremely hydrophobic coating that does not interfere with signaltransmission or reception.

[0023] A need also exists for a composition which forms a hydrophobicsurface useful as a surface for articles which could benefit fromhydrophobic properties, for example, vehicular surfaces, architecturalsurfaces, outdoor furniture, household goods, and kitchen and batharticles.

SUMMARY OF THE INVENTION

[0024] According to the present invention, extremely hydrophobiccoatings are provided. According to an embodiment of the presentinvention, the invention provides a durable, weatherable, anderosion-resistant hydrophobic coating. The coatings of the presentinvention can be used on a signal transmitter or receiver, for example,a microwave, infra-red, light, radar, electromagnetic, or the likeemitter or receiver such as a radome. The coatings of the invention donot adversely affect reception or transmission of a signal.

[0025] According to another embodiment of the present invention, aprocess is provided for forming an extremely hydrophobic coating on asurface of an article. An embodiment of the present invention is basedon the discovery that methods can be provided to coat laboratory vesselswith an extremely hydrophobic coating at a cost of only a few cents perthousand vessels.

[0026] According to embodiments of the present invention, a surface iscoated with a composition which includes or provides a reaction product,for example, a polymerization product, of a fluorinated reactant, forexample, a fluorinated monomer containing from about 3 to about 20carbon atoms and at least one terminal trifluoromethyl group. Accordingto embodiments of the invention, the coating composition also includes ahardenable material, for example, a urethane resin or TEFLON AF fromDuPont. Hardenable materials that may be employed includenon-fluorinated hardenable resins, fluorinated hardenable resins, andperfluorinated hardenable resins. The resulting surfaces are extremelyhydrophobic and highly resistant to removal by weathering and/orsolvents.

[0027] Herein, the term “fluorinated” includes both perfluorinated andnon-perfluorinated monomers and/or polymers. The present inventionrelates to fluorinated compositions, coatings, and coated surfaces whichmay be part of or parts of laboratory vessels, signal transmitters,signal receivers, signal reflectors, radomes, vehicular surfaces,architectural surfaces, outdoor furniture, household goods, kitchenarticles, kitchen surfaces, bathroom articles, bathroom surfaces,antennae, microwave antennae, dishes, reflectors, signs, visualsignaling devices, scanner windows, lenses, liquid crystal displays, andvideo displays. In addition, the present invention relates to processesof coating small article surfaces, for example, laboratory vessels, withnominal solvent loss.

[0028] Processes of forming the extremely hydrophobic coatings of thepresent invention may include applying a solution, suspension or otherliquid containing a coating composition and allowing the solution,suspension or other liquid to harden, dry and/or cure on a surface. Thecoating composition includes a trifluoromethylated agent, which may be areactant, a monomer, a reaction product, and/or a polymerizationproduct. The present invention also provides a method wherein a solutionor suspension of such agent is partially, selectively or conformallycoated onto at least a portion of a surface of an article, for example,a laboratory vessel, a radar dish, a radome, a windshield, a rainshield,a vehicular surface, an architectural surface, outdoor furniture, ahousehold good, a kitchen article, a kitchen surface, a bath article, abathroom surface, an antenna, a microwave antenna, a dish, a reflector,a sign, a visual signaling device, a scanner window, a lens, a liquidcrystal display, and/or a video display. Then, the composition includingthe agent is subsequently hardened, dried, and/or cured to removesolvent and/or suspension medium. The coatings provide surfacesexhibiting extremely low surface energies and, for some cases,preferably also provide a high resistance to solvent removal. Somecompositions according to the present invention may desirably be removedwith one or more organic solvent, for example, with methylethylketone(MEK).

[0029] A surprising discovery about the economics and commercial successof coating low cost, especially one-time-use, articles withfluoropolymer coatings is that process efficiency in recovering carriersolvents can be a more important factor than the relatively high cost ofthe coating fluoropolymers. While high quality unsaturatedfluoromonomers currently can cost $250 (US) to over $1000 (US) per poundin bulk quantities, articles such as pipette tips may only require 10 to20 milligrams of fluoropolymer per thousand pipette tips at a currentcost of less than 10 cents per thousand. Conventional coating/washingequipment, for example, equipment from Renzacci of America Inc.,Absecond, N.J., and from Fluoromatic Ltd., Villa Park, Ill. andprocesses that are designed to recover solvents, can consume over 25grams of solvent per thousand pipette tips at a current cost of aboutfive cents per gram or $1.25 (US) per thousand. In many situations,particularly coating methods using expensive perfluoropolymers, this isan unacceptable added cost to articles otherwise costing only a fewdollars per thousand to manufacture. According to the present invention,solvent loss is significantly reduced compared to the conventionalmachines and processes.

[0030] According to some embodiments of the invention, a hydrophobiccoating may be formed from a coating composition of the inventionapplied or co-injected as a resin, powder, particle or mixture which isdried, melted, sintered, fused cured or otherwise formed on a surface ofan article.

[0031] Moreover, the present invention is based on the discovery thatlaboratory vessel surfaces of low surface energy can be provided bycoating a solution, suspension, other liquid, resin, powder, particle ormixture of a trifluoromethylated agent according to the invention,admixed with microscopic particles and/or fibers. In some embodiments,foaming and/or pore-forming agents may additionally, or alternatively,be admixed with the coating compositions of the present invention. Thetrifluoromethylated agent may include a trifluoromethylated reactant,monomer, reaction product and/or polymerization product. Upon subsequentdrying, melting, solidifying, sintering, fusing or curing of the coatingformulation, a laboratory vessel is produced exhibiting extraordinarilyhigh contact angles to aqueous liquids.

[0032] The present invention is also based on the discovery thatcoatings of trifluoromethylated agents containing 3 to 20 carbon atomsand at least one terminal trifluoromethyl group are extremelyhydrophobic and can provide populations of 30% by area or greater oftrifluoromethyl groups on exposed coating surfaces. According to thepresent invention, a reaction product of a reactant trifluoromethylatedagent may be coated from a formulation onto at least a portion of anoperational surface of a laboratory vessel, for example, a vesselsurface which contacts or restrains a liquid sample. The coatings havetightly packed, exposed trifluoromethyl groups.

[0033] According to some embodiments, at least about 30% of the area ofthe exposed coating surface is covered by trifluoromethyl groups.According to more preferred methods of the invention, the exposedcoating surface is covered with a population of trifluoromethyl groupsof from about 50% to 100% by area of the surface. According to someembodiments, at least about 15% by area of the exposed coating surfaceis covered by trifluoromethyl groups and the coating includes ahardenable resin in addition to a reaction product of atrifluoromethylated agent.

[0034] According to the present invention, the coating compositioncomprises a trifluoromethylated agent comprised of a fluorocarbon,hydrofluorocarbon, epoxy, urethane, silicone, acrylic or other materialthat has a terminal trifluoromethyl group and contains from about 3 toabout 20 carbon atoms. Preferably, coatings made from such compositionsexhibit tightly packed trifluoromethyl groups on the exposed coatingsurface. According to some embodiments of the invention, coatingpolymers made from substantially non-branched fluorinated monomershaving carbon chains of from about 3 to about 20 carbon atoms in length,and more particularly from about 6 to about 12 carbon atoms in length,enable a dense packing of the terminal trifluoromethyl groups and thuscan form hydrophobic surfaces of very low surface energy, havingcritical surface tensions of about 10 dynes/cm or lower at 20° C., andhaving high resistance to solvent removal and low retention ofbiological samples.

[0035] According to yet other embodiments of the invention, laboratoryvessels and other articles are coated with hydrophobic coatingformulations containing terminal trifluoromethyl groups and optionallyfurther containing reaction products, polymers, reactants, polymerizablemonomers and/or other additives which also become incorporated in thehydrophobic coatings.

DETAILED DESCRIPTION OF THE INVENTION

[0036] According to embodiments of the present invention, an extremelyhydrophobic coating can be formed on the surface of an article andcomprises the reaction product of a reactant containing a terminaltrifluoromethyl group. According to embodiments of the presentinvention, an extremely hydrophobic coating can be formed from acomposition consisting essentially of the reaction product of a reactantcontaining a terminal trifluoromethyl group with or without a hardenableresin, for example, a urethane resin. Particular articles which can becoated according to the present invention include those having anoperational surface comprising plastic, sintered material, wovenmaterial, textured material, semiconductor, glass, ceramic, or metal, ora primed or pre-coated surface. The invention can also be used onoperational surfaces which are porous, smooth, rough, pitted, foamed,grooved, cross-hatched, striated, or having patterned physical features.

[0037] Laboratory vessels according to an embodiment of the presentinvention have at least one operational surface. Many vessels accordingto the invention have at least one interior wall which defines areservoir portion for containing a volume of liquid, and at least oneopening in communication with the reservoir portion. According to someembodiments of the invention, a laboratory vessel having an interiorwall and an opening is coated on the interior wall and on the areasurrounding and forming the opening, with a polymer coating according tothe invention.

[0038] According to embodiments of the present invention, methods areprovided for forming extremely hydrophobic coatings on small articlessuch as laboratory vessels. Measures to curtail fluorinated solventlosses, according to the present invention, focus on better containment,improved solvent recovery, and reduced solvent vap or pressurethroughout the coating operation. According to embodiments of theinvention, the general design of the Renzacci Patriot 350, from Renzacciof America, may be employed for the coating machine and process of thepresent invention, but with some major modifications. According to thepresent invention, it has been determined that rubber and silicone sealsare significantly not leak-proof to fluorocarbon solvents. According tothe present invention, sealing means comprising a rubber derived fromvinylidene fluoride and hexafluoropropene, for example, VITON™ seals aresubstituted for other rubber or silicone seals. The generally lowerpermeability of VITON™ seals to hydrophobic gases such as methane andtetrafluoromethane prevent a significant amount of fluorocarbon solventand/or gas loss as a result of a coating process.

[0039] Metal tubing and swaged fittings are preferred over plasticpiping and threaded pipe connections. If the Renzacci machine ismodified to form an apparatus according to the present invention, thecarbon “recovery” system of the Renzacci model is preferably eliminated.

[0040] According to embodiments of the present invention, solventrecovery is enhanced by lowering the cooling coil temperature and byslowing the air flow over the coils. Longer recovery times areprogrammed to further improve solvent recovery according to embodimentsof the present invention. According to embodiments of the invention,significant benefits in reducing solvent loss are achieved by operatingthe entire coating cycle at temperatures that keep solvent vaporpressure low relative to atmospheric pressure, that is, at about orbelow atmospheric pressure. Although removing solvent from wettedarticles according to the invention requires somewhat more time, theincreased cost of machine time is only hundredths of a cent per thousandpipette tips. Solvent consumption, however, is reduced to only barelydetectable levels, providing overall savings of more than $60 (US) percycle.

[0041] According to embodiments of the present invention, a process isprovided wherein laboratory vessels can be coated with a compositionwhich forms a coating having at least a 15% by area trifluoromethylsurface, and solvent loss resulting from the process of less than 20grams of fluorosolvent lost per pound of processed laboratory vessels.More preferably, solvent loss resulting from the process is less than 10grams of fluorosolvent lost, more preferably less than 5 grams offluorosolvent lost, per pound of processed laboratory vessels. Even morepreferably, fluorosolvent loss according to an embodiment of the presentinvention is only one gram of fluorosolvent lost per one pound ofprocessed laboratory vessels.

[0042] According to embodiments of the present invention, a process isprovided wherein articles, for example, laboratory vessels, can becoated with a composition which forms a coating having at least a 15% byarea trifluoromethyl surface, and solvent vapor pressure within thecoating chamber is maintained substantially below atmospheric pressure.Preferably, solvent vapor pressure within the coating chamber ismaintained at below about 25% of atmospheric pressure, more preferably,at below about 10% of atmospheric pressure, for example, below about 5%of atmospheric pressure. Even more preferably, solvent vapor pressure ismaintained at less than 1% of atmospheric pressure. Temperature controlcan be used to maintain low pressure. The solvent loss is substantiallyminimized according to the process of the present invention whereinafter coating the articles the seal of the sealed chamber is brokenwhile the vapor pressure within the chamber is below atmosphericpressure, preferably below about 25% of atmospheric pressure.

[0043] According to the present invention, laboratory vessels areprovided with coatings having at least a 15% surface area population oftrifluoromethyl groups by a process wherein solvent temperature ismaintained substantially below its boiling point during the coating andsolvent recovery process. Preferably, a fluorinated solvent is used.Preferably, solvent temperature is maintained below 75%, for example,below 50% of the absolute value of the difference between the boilingpoint of the solvent and 25° C. For example, if the solvent has aboiling point of 85° C., the temperature is preferably maintained at orbelow 70° C., which is at or below 75% of the absolute differencebetween 85° C. and 25° C. More preferably, solvent temperature ismaintained below 25% of the absolute value of the difference between theboiling point of the solvent and 25° C. Cooling water chillers or heatexchangers can be used, for example, to lower the temperature of thecoating solution or suspension.

[0044] Articles such as laboratory vessels to be coated according to aprocess of the present invention may contain or consist of plastic,metal, or glass. Preferred materials used to manufacture the coatedlaboratory vessels of the present invention include polypropylene,polyethylene, polyethyleneterephthalate, polystyrene, polycarbonate andcellulosics. More expensive plastics such as polytetra-fluoroethyleneand other fluorinated polymers may be used. Some vessels made from theseplastics are hydrophobic without any additional coating. Herein, theterm “hydrophobic” refers to a surface exhibiting an average surfaceenergy of about 40 dynes/cm or less. Because polypropylene isinexpensive and quite hydrophobic itself, it is a particularly preferredmaterial for laboratory vessels, including pipette tips, used forhandling and transporting minute and precise amounts of biologicalsample.

[0045] In addition to the materials mentioned above, examples of othersuitable materials for the laboratory vessels of the present inventioninclude polyolefins, polyamides, polyesters, silicones, polyurethanes,epoxies, acrylics, polyacrylates, polyesters, polysulfones,polymethacrylates, polycarbonate, PEEK, polyimide, polystyrene, andfluoropolymers such as PTFE Teflon®, FEP Teflon®, Tefzel®,poly(vinylidene fluoride), PVDF, and perfluoroalkoxy resins. Glassproducts including silica glass are also used to manufacture laboratoryvessels. One exemplary glass product is PYREX®(available from CorningGlass, Corning, N.Y.). Ceramic or oxide surfaces can be coated accordingto embodiments of the invention. Cellulosic products such as paper andreinforced paper containers can be coated to form coated laboratoryvessels according to the invention. Metal surfaces can be coatedaccording to the invention, as can surfaces of glass, silicon, siliconcompounds or ceramics that have or have not been primed with silanecontaining materials or other adhesion promoting materials. Primedmetal, primed glass, primed ceramic and primed oxide surfaces can becoated according to embodiments of the invention. Vessel surfaces thathave been pre-coated with epoxies, silicones, urethanes, acrylics, orother materials can also be coated according to embodiments of theinvention.

[0046] Although some wash-off of polymerized coating material or coatingmonomer might be expected after repeated usage, the coatings of thepresent invention do not measurably wash off most laboratory vesselsurfaces. It is believed that little if any wash-off occurs because thecoating solution causes softening and swelling of the vessel material,especially in uncross-linked plastics, and enables entanglement ofcoating and vessel substrate molecules allowing strong Van der Waals andother bonding forces which hold the prepolymerized product where appliedto an operational surface of the vessel. The linear swelling of manypolymers and elastomers, including some fluoroelastomers and somesilicones, is reported in Table 8 of the 1996 Technical Informationsheet for Vertrel™ XF, available from DuPont's Polymer ProductsDivision, Wilmington, Del. Little if any wash-off occurs from othervessel materials because of the extremely low solubility of the coatingsof the present invention in most solvents and limited solubility influorinated solvents. Preferably, even exposure to water wash conditionsof 1500 psi causes no substantial reduction in hydrophobic properties ofthe coating or material having a surface of the present invention.

[0047] According to some embodiments of the present invention,hydrophobic reaction products having terminal trifluoromethyl groups arecoated from a fluorinated agent/fluorosolvent solution or suspensiononto linear, hydrophobic, essentially uncrosslinked polymers such aspolyolefins and TEFLON®and show particular resistance to removal even bychlorinated solvents. According to the present invention, swelling ofthe polyolefin surface during application of the fluorinated agentsolution or suspension and subsequent entanglement of the reactionproduct, for example, polymerization product, at the interface, resultin strong hydrophobic bonds between the coating and the polyolefinsurface. Surprisingly, the coatings according to embodiments of theinvention are not measurably removed, even with chloroform orchloroethene.

[0048] According to some embodiments of the invention, the laboratoryvessel comprises a microscope slide or other substantially flat devicehaving an operational surface at least partially coated with a coatingformulation according to the invention. According to some embodiments ofthe invention, a delineated area of a laboratory vessel surface, forexample, a portion of the surface of a microscope slide, is not coatedwith the coating formulation, but is instead surrounded by the coating.The coating thus forms a boundary to restrain, contain or isolate afluid sample on the non-coated area of the surface, while adjacentsurfaces remain free of liquid sample, thus isolating and facilitatingchemical and biological reactions as well as improving sample recovery.The uncoated locations may have surfaces that, for example, are reactiveor have specific affinities, optimize the sample volume to area ratio,or restrict sample movement during some vessel motion. The uncoatedregion may be surrounded by a hydrophobic coating material according tothe invention which comprises microparticles and the reaction product,for example, the polymerization product, of a trifluoromethyl-containingreactant, for example, a trifluoromethyl-containing monomer.

[0049] According to some embodiments of the invention, the operationalsurface of a vessel such as a microscope slide is partially coated witha hydrophobic coating formulation according to the invention andpartially coated with nonfluorinated material in delineated regions toisolate or constrain the position of a liquid sample to prescribedlocations that do not contain the hydrophobic coating formulation.

[0050] According to embodiments of the invention, an operational surfacecomprises a sample retaining barrier of a rough surface compositecoating according to the invention. The barrier may isolate and restrainan aqueous sample. Surrounding the composite coating may be a smoothcoating material which does not contain a sufficient amount ofmicroparticles and does not exhibit surface roughness. The surroundingsmooth coating permits the run-off of non-aqueous liquids therefrom,such as organic solvents, for example, acetone or xylene.

[0051] According to some embodiments, a laboratory vessel is providedwith a low surface energy coating of the present invention and furthercomprises a second coating. The second coating comprises the reactionproduct, for example, the polymerization product, of a secondfluorinated reactant, for example, a fluorinated monomer. The secondfluorinated reactant preferably has from about 3 to about 20 carbonatoms, at least one terminal trifluoromethyl group, and is combined witha surface roughening agent, for example, a micropowder which providesthe second coating with a rough surface. The second coating has anexposed surface area populated with 30% by area or more trifluoromethylgroups and a surface energy of about 22 dynes/cm or less at 20° C. Thesecond coating forms a continuous sample retaining barrier for retainingan aqueous sample within the barrier, and the low surface energy coatingis substantially free of surface roughness and surrounds the secondcoating.

[0052] Articles other than laboratory vessels can also be coated withtwo different coating compositions according to embodiments of thepresent invention. According to some embodiments of the presentinvention, an article is coated with a first composition and then with asecond, different, composition. At least one of the coatings, forexample, the first coating, preferably comprises the polymerizationproduct of at least one fluorinated monomer. At least one of thecoatings can comprise the polymerization product of tetrafluoroethylene.At least one of the coatings can comprise the polymerization product ofperfluoro-2,2-dimethyl-1,3-dioxole (PDD). At least one of the coatingscan comprise the polymerization product of tetrafluoroethylene and PDD.Preferably, both coatings provide a trifluoromethyl group surface areapopulation of about 15% by area or greater, more preferably, of about30% by area or greater.

[0053] According to embodiments of the invention, regions on a surfaceof a laboratory vessel such as a microscope slide are used to isolate orconstrain aqueous sample, and the regions are defined by a first coatingcomprising microscopic particles and the reaction product of atrifluoromethyl-containing reactant. The first coating may surround aportion of a surface coated with a second coating wherein the secondcoating comprises the reaction product of a trifluoromethyl-containingreactant. The microparticle-containing coating provides a greaterhydrophobicity to aqueous liquids and thus a greater water repellingnature than the region coated with the polymerization product coatingthat does not contain the microparticles.

[0054] In some embodiments of the present invention, microscopic fiberssuch as cellulose or glass microfibers may be used with or in place ofmicroparticles to provide surface roughness and preferably contactangles to water of about 150° and greater. Preferably, cellulose and/orglass microfibers are used which have average diameters of from aboutone to about 20 microns and lengths from about 20 to several hundredmicrons. The microfibers can be admixed to increase the mechanicalstrength of the coating.

[0055] According to embodiments of the invention, rough hydrophobicsurfaces having a high repellency to water may be produced by employingfoaming and/or pore-forming agents in the compositions and processes ofthe invention. Foaming and pore-forming agents that may be used includespirocarbonates, diazo compounds, compressed gases, dissolved gases,volatile liquids, and combinations thereof. The agents may be activatedby heat, light, or vacuum during the drying, curing and/or hardening ofthe coating composition.

[0056] According to embodiments of the invention, regions on a surfaceof a laboratory vessel such as a microscope slide are used to isolate orconstrain an organic solvent-based liquid sample, and the regions aredefined by a coating comprising the reaction product of atrifluoromethyl-containing reactant, surrounding a portion of thesurface coated with a formulation comprising microparticles and thereaction product of a trifluoromethyl-containing reactant. Themicroparticle-containing coating provides a greater affinity to organicsolvent-based liquids than the region coated with the reaction productcoating not containing the microparticles.

[0057] A preferred coating is provided by adhering a surface rougheningagent, for example, a micropowder, to the surface of a reaction productaccording to the present invention, wherein the coating has an exposedsurface area populated with 30% or more trifluoromethyl groups. Apreferred coating can be formed with a surface roughening agent having asurface area populated with 30% by area or more trifluoromethyl groups,wherein the surface roughening agent is adhered to a hydrophobicsurface. The adherence of the surface roughening agent to the surfacemay be due to one or more mechanisms including, but not limited to,sintering the agent onto the surface, curing a component of the surfaceand/or a component of the agent, melting the surface and/or the agent,and the like, or any combination thereof. The surface roughening agent,for example, a micropowder, can be dusted onto the surface.

[0058] The present invention also provides processes of preparingsurface roughening agent-containing hydrophobic surfaces. According toan embodiment of the invention, a hydrophobic coating formulation isapplied to a surface of an article to form a coating having an exposedsurface area populated with at least 30% by area trifluoromethyl groups.Then, fluidized hydrophobic surface roughening agent microparticles areapplied and adhered to the coating to provide a rough surface having anexposed surface area populated with at least 30% by area trifluoromethylgroups.

[0059] The adherence of the agent to the coating may be due to one ormore mechanisms including, but not limited to, sintering the agent ontothe surface, curing a component of the coating and/or a component of theagent, melting the coating and/or the agent, and the like, or anycombination thereof.

[0060] According to an embodiment of the invention, a hydrophobiccoating formulation is applied to a surface of an article to form acoating having an exposed surface area populated with at least 30% byarea trifluoromethyl groups. Then, fluidized hydrophobic surfaceroughening agent microparticles having an exposed surface area populatedwith at least 30% by area trifluoromethyl groups are adhered to thecoating to provide a surface having a population of trifluoromethylgroups of 30% by area or more. The adherence of the agent to the coatingmay be due to one or more mechanisms including, but not limited to,sintering the agent onto the surface, curing a component of the coatingand/or a component of the agent, melting the coating and/or the agent,and the like, or any combination thereof.

[0061] According to some preferred embodiments of the invention,laboratory vessels are provided having an operational surface coatedwith a polymer comprising the polymerization product oftrifluoromethyl-terminated, substantially unbranched and fluorinatedmonomers containing from 6 to 12 carbon atoms. Coatings made from suchproducts are extremely hydrophobic, oleophobic, and highly resistant tosolvent removal and biological sample retention.

[0062] A particularly preferred coating solution for forming coatingsaccording to the invention comprises the polymerization product of atrifluoromethyl terminated, substantially unbranched perfluorooctylmonomer. Coating solutions containing at least about 50% by weight of aproduct of such a perfluorooctyl monomer are particularly preferred forprinting applications.

[0063] The coating compositions of the present invention may be dilutedwith an appropriate solvent or medium to obtain a coating solids contentof from about 0.01% by weight to about 50% by weight, preferably fromabout 0.1% by weight to about 2% by weight, depending upon theapplication technique and desired coating properties.

[0064] According to an embodiment of the present invention, a coatingcomposition is provided for forming an extremely hydrophobic coatingsurface on the surface of an article, wherein the composition includes afluorosilane, a fluorinated acid anhydride or fluoroanhydride, and afluorinated solvent. The fluorosilane may preferably be used in anamount of from about 0.1% by weight to about 50% by weight, for example,2% by weight, based on the weight of the composition. The fluorosilaneis preferably a fluoroalkylsilane. More preferably, the fluorosilane mayinclude a fluoroalkyl alkoxysilane, for example, perfluorooctyltrimethoxysilane. The fluorinated acid anhydride or fluoroanhydridepreferably is capable of a condensation reaction with an oxide surfaceto form an extremely hydrophobic surface, and preferably reacts underambient conditions or under heat. The fluorinated acid anhydride orfluoroanhydride may comprise, for example, trifluoroacetic acidanhydride, trifluorobutyric acid anhydride, and combinations thereof,both available from Aldrich Chemicals. The fluorinated solventpreferably has a boiling point above 100° C. Preferred fluorinatedsolvents include FC 70 (boiling point of 215° C.), and FC 40 (boilingpoint 155° C.), both available from 3M.

[0065] The terminal trifluoromethyl groups of the coating polymer ormonomer preferably constitutes the entire operational surface of thecoating. According to preferred embodiments of the invention, thepolymer coating is applied in a manner such that the exposed coatingsurface comprises from about 30% by area to about 100% by areatrifluoromethyl (—CF₃) groups. In other words, of the molecules andsubstituent groups making up the exposed operational surface of thecoating, from about 30% by area to 100% by area of the exposed surfacearea of the coating is made up of —CF₃ groups. The exposed surface ofthe coating exhibits an extremely low surface energy which can approachabout six dynes/cm, depending upon the percentage or “population” of—CF₃ groups making up the exposed surface of the coating and the vesselmaterial coated according to the invention. In more preferredembodiments of the invention, from about 50% by area to 100% by area ofthe exposed surface is populated with trifluoromethyl groups, and evenmore preferably, at least about 75% by area is populated withtrifluoromethyl groups.

[0066] The hydrophobicity and solvent resistance of the operationalsurface coating of the invention depends on a number of factorsincluding the material of the laboratory vessel which is coated and theamount or population of terminal trifluoromethyl groups present on theexposed surface of the coating. For example, it has been determinedaccording to the invention that when an operational surface of apolypropylene vessel is coated with a hydrophobic polymer solution toform a coating comprising 30% by area or moretrifluoromethyl-terminated, substantially unbranched perfluorinatedmonomer having from 6 to 12 carbon atoms, the coating exhibits a surfaceenergy of below 20 dynes/cm with high resistance to solvent removal andlow retention of biological samples.

[0067] It has also been determined according to the invention that whenan operational surface of a polypropylene vessel is coated with ahydrophobic polymer solution to form a coating comprising 50% by area ormore trifluoromethyl-terminated, substantially unbranched perfluorinatedmonomer having from 6 to 12 carbon atoms, the coating exhibits a surfaceenergy of below 15 dynes/cm with high resistance to solvent removal andlow retention of biological samples.

[0068] It has also been determined according to the invention that whenan operational surface of a polypropylene vessel is coated with ahydrophobic polymer solution to form a coating comprising 80% by area ormore trifluoromethyl-terminated, substantially unbranched perfluorinatedmonomer having from 6 to 12 carbon atoms, the coating exhibits a surfaceenergy of about 10 dynes/cm with high resistance to solvent removal andlow retention of biological samples.

[0069] It has also been determined according to the invention that whenan operational surface of a polypropylene vessel is coated with ahydrophobic polymer solution to form a coating comprising 100% by areaor more trifluoromethyl-terminated, substantially unbranchedperfluorinated monomer having from 6 to 12 carbon atoms, the coatingexhibits a surface energy of below 10 dynes/cm or lower with highresistance to solvent removal and low retention of biological samples.

[0070] The most hydrophobic properties are achieved when the coating hasan exposed surface consisting entirely of trifluoromethyl (—CF₃) groups,that is, 100% by area, with no other substituent groups exposed at thesurface.

[0071] According to some embodiments of the invention, branchedfluoroalkyl monomers containing terminal trifluoromethyl groups may alsobe used as reactive monomers or polymerized product in the coatingsolutions used according to the present invention. An example of asuitable branched monomer for such purposes is a perfluorinatediso-octyl monomer having two terminal trifluoromethyl groups.

[0072] According to embodiments of the invention, the carbon chainlength of the trifluoromethyl-containing monomers used to form thepolymer coatings of the invention, and any functional groups used toform linkages between the fluoropolymer and the laboratory vessel,should be selected to provide an exposed surface of the coating whichmainly comprises —CF₃ groups. The —CF₃ groups, which provide extremelyhydrophobic properties, prevent liquids and samples contained in thevessel from infiltrating the exposed coating and reacting with theintermediate carbon groups and linkage groups of the polymerizedmonomer. Such infiltration is particularly prevented when the coatingconsists of monomers of substantially uniform length of greater than 6carbon atoms, rather than a mixture of monomers of substantiallydifferent lengths.

[0073] According to embodiments of the invention, a polymer coatingformed from a fluoroalkyl methacrylate monomer which has the chemicalformula C₇F₁₅CH₂OCOC(CH₃)═CH₂ is provided. Coatings made with thepolymerized product of this monomer or similar fluoroalkyl monomershaving a trifluoromethyl group, have exposed coating surfaces comprisingtightly packed terminal—CF₃ groups. The resultant coating has a lowsurface energy, or critical surface tension, which can be as low asabout 6 dynes/cm at 20° C. depending upon the population oftrifluoromethyl groups on the exposed surface and depending upon thematerial of the vessel which is coated. However, when a surfacepopulation of 100% by area trifluoromethyl groups is achieved, thevessel material is irrelevant to the hydrophobicity of the surface.

[0074] As the packing of terminal trifluoromethyl groups increases, thesurface energy of the packed surface decreases, such that coatingshaving the lowest critical surface tension have the closest packed —CF₃groups. The replacement of a single fluorine atom by a hydrogen atom ineach terminal trifluoromethyl group of such a surface would more thandouble the critical surface tension of the surface. Critical surfacetensions of teflon vessels and teflon coated vessels are only as low asabout 18 dynes/cm at 20° C. because such surfaces mainly comprise —CF₂—groups. Although it is difficult to obtain an exposed surface entirelycomposed of tightly packed —CF₃ groups, extremely low surface tensionscan be achieved by the formation of exposed coating surfaces whichcontain 30% or more, by surface area, —CF₃ groups. Preferably, anexposed surface having 50% or more —CF₃ groups can be achieved accordingto the processes of the present invention. These processes tend toresult in coatings having critical surface tensions ranging from about 6dynes/cm to about 22 dynes/cm when formed on hydrophobic vesselmaterials.

[0075] Critical surface tensions, also referred to as surface energies,of as low as about 6 dynes/cm can be obtained according to the processesof the present invention, depending upon which terminal trifluoromethylgroup-containing polymer or mixture of polymers is used to form thehydrophobic coating, the population of trifluoromethyl groups on theexposed surface, and the material of the vessel to be coated. Accordingto embodiments of the invention wherein the exposed surface area of thehydrophobic coating material is populated with from about 50% by area toabout 100% by area trifluoromethyl groups, surface energies of about 10dynes/cm or less can be provided, particularly if the coating is formedon a polypropylene or other substantially hydrophobic laboratory vesselmaterial, for example, a vessel material which exhibits a surface energyof 40 dynes/cm or less. Such surface energies are even lower than thoseof Teflon® which generally provides a surface energy of from about 18.5to about 20 dynes/cm. Although Teflon® is formed from polymerized fullyfluorinated monomers, most of the surface structure of a Teflon® coatingconsists of —CF₂— groups as opposed to closely packed terminaltrifluoromethyl (—CF₃) groups. Even the most hydrophobic forms ofTeflon®, FEP Teflon® and PFA Teflon®, which comprise mixtures of fullyfluorinated polypropylene and polyethylene polymerized monomers, onlyprovide surface energies of about 16.5 dynes/cm. As with other forms ofTeflon®, the exposed surface of an FEP Teflon® coating consists mainlyof —CF₂— groups as opposed to closely packed terminal trifluoromethyl(—CF₃) groups. Teflon® and FEP Teflon®, are available from DuPontPolymer Products Department, Wilmington, Del.

[0076] According to the present invention, lower surface tensions areobtained when the coating polymer comprises the polymerization productof a perfluoroalkyl monomer, when compared to coatings comprising theproduct of a partially non-fluorinated monomer. Substantiallynon-branched fluoroalkyl and perfluoroalkyl ethylenically unsaturatedmonomers are preferred for producing the coating polymers of theinvention. According to other embodiments, a methacrylate group is usedas a preferred ethylenically unsaturated monomer for making thepolymeric coating material of the invention. Other monomers which can beused include silicones, epoxies and urethanes. Other reactants which maybe used include anhydrides, amines, polyols, vinyls, vinyl ethers, andmixtures thereof. Polymers made from mixtures of acrylates and epoxiesor of acrylates and silicones are particularly preferred according tosome embodiments of the invention. Polymeric coating materialscomprising urethane monomers and/or polymers are preferred for someapplications wherein a durable coating is needed.

[0077] According to embodiments of the present invention, articles canbe provided with a coating thereon comprised of a prepolymerizedfluoroalkyl, or preferably perfluoroalkyl, ethylenically unsaturatedmonomer having a terminal trifluoromethyl group. More particularly, thepresent invention relates to such a coating which consists essentiallyof a polymerization product of a fluoroalkyl or perfluoroalkylethylenically unsaturated monomer having a terminal trifluoromethylgroup and an average carbon atom chain length of from 3 to about 20atoms, more preferably from about 6 to about 14 atoms, and optionally adurable resinous component such as a urethane or polyurethane component.

[0078] According to a preferred embodiment of the present invention,prepolymerized terminal trifluoromethyl-containing monomers having auniform pendant group length of from 8 to 10 carbon atoms andsubstantially free of branching can be deposited on laboratory vesselsto form coatings with low surface energies and critical surface tensionsof about 10 dynes/cm or less. The coatings also exhibit exceptionalresistance to many solvents with the exception of substantiallyfluorinated solvents. Coating solutions containing polymers of suchmonomers produce a highly ordered, densely packed polymer with apredominantly trifluoromethyl surface.

[0079] Solutions of polymers made from monomers having terminaltrifluoromethyl groups are commercially available. One solution whichcan be used to form polymeric hydrophobic coatings according to theinvention is available from The 3M Company as FC-722. Othertrifluoromethyl group-containing polymer solutions in fluorosolvents areavailable from Cytonix Corporation of Beltsville, Md. as thePerFluoroCoat and FluoroPel products lines. The coating solutions usedaccording to embodiments of the present invention comprisefluoropolymers having terminal trifluoromethyl groups. The solutions canbe used full strength but may be diluted with a fluorosolvent to formlow concentrations of coating polymer. The polymer solution used to makethe coatings of the invention preferably have a coating polymer contentof from about 0.01% by weight to about 50% by weight.

[0080] Methods of making fluoropolymer coating solutions or suspensionsfor use with the invention comprise prepolymerizing a fluoroalkylethylenically unsaturated monomer having a terminal trifluoromethylgroup to form a polyfluoroalkyl polymer, and dissolving or suspendingthe polymer in a fluorinated solvent. When making such solutions, thefluoroalkyl ethylenically unsaturated monomer preferably has a carbonchain length of from about 3 to about to 20 carbon atoms, with carbonchain lengths of from about 6 to about 12 atoms being more preferred.Carbon chain lengths of from 8 to 10 atoms are particularly preferred.Mixtures of different fluoroalkyl ethylenically unsaturated monomershaving different carbon chain lengths may be employed, however, when thepolymerized monomers have essentially uniform carbon chain lengths,hydrophobic coatings of extremely low and repeatable surface tension canbe provided.

[0081] According to embodiments of the invention, hydrophobic coatingsare provided which may preferably comprise, and more preferably consistessentially of, a polymerization product of a substantially non-branchedperfluoroalkyl monomer. Coatings according to the invention may comprisepolymerized products of monomers having terminal trifluoromethyl groups,including fluorinated or perfluorinated monomers such as hexylethylenically unsaturated monomers, heptyl ethylenically unsaturatedmonomers, octyl ethylenically unsaturated monomers, nonyl ethylenicallyunsaturated monomers, decyl ethylenically unsaturated monomers, undecylethylenically unsaturated monomers, and dodecyl ethylenicallyunsaturated monomers. Mixtures of two or more different monomers mayalso be used and are preferred when it is desired to adjust surfaceenergy properties to precise values.

[0082] The coatings of the present invention may comprise or consistessentially of a polymerization product of a fluoroalkyl ethylenicallyunsaturated monomer having a terminal trifluoromethyl group and a carbonchain length of from 3 to 20 atoms, preferably from 6 to 12 carbon atomsin length, and more preferably from 8 to 10 carbon atoms in length. Inparticular, polymerization products of fluoroalkyl methacrylates arepreferred. According to some embodiments of the invention,polymerization products of perfluorohexyl methacrylate, perfluoroheptylmethacrylate, perfluorooctyl methacrylate, perfluorononyl perfluorodecylmethacrylate, perfluoroundecyl methacrylate or perfluorododecylmethacrylate, and mixtures thereof, are preferred. Acrylates of suchperfluoroalkyls are also preferred. According to one particularlypreferred embodiment, the polymer coating consists essentially of apolymerization product of perfluorooctyl methacrylate.

[0083] Exemplary materials for making the coatings of the presentinvention include PerFluoroCoat and FluoroPel, both available fromCytonix Corporation, the fluorinated materials FC-722, FX-13, FX-14,FX-189, L-9187, L-9186, Fluorel™ FC 2174 and Fluorel™ FC 2181, allavailable from Commercial Chemicals Division/3M, St. Paul, Minn.silastic fluorosilicone rubbers from Dow Corning STI identified asLS-2249U, LS-2332U, LS-2840 and LS-2860, and fluorinated materials fromDuPont including materials traded under the name ZONYL.

[0084] The solvent for the coating solutions used according to theinvention may comprise a fully fluorinated non-branched fluorocarbonhaving a carbon chain length of 7 or 8 carbon atoms. Such a solventexhibits a boiling point of about 80° C. Perfluorinated fluorocarbonsolvents are preferred according to some embodiments of the invention.

[0085] According to embodiments of the invention, preferred fluorinatedsolvents include the Fluorinert) line of fluorinated solvents, FC-71,FC-75, FC-40, FC-70, FC-77 and FC-84, all from the 3M Company. Otherfluorinated solvents which may be used include Vertrel® XF (C₅H₂F₁₀) orFreon TF from DuPont, Wilmington, Del. the fluorinated polyethers HT70,HT85, HT90, HT100, HT110, HT135, HT200, HT230, HT250 and HT270, and theperfluorinated polyethers sold as GALDEN, all from Ausimont USA, Inc.The Ausimont USA, Inc. solvent designations indicate the boiling pointof each solvent. Higher boiling solvents, for example, HT270 and HT250,would form coatings requiring more heat to dry than coatings made withthe lower boiling solvents, for example, HT70. The lower boilingAusimont USA, Inc. solvents more rapidly evaporate when compared to thehigher boiling solvents.

[0086] Other fluorocarbon solvents may be used and typically haveboiling ranges of from about 30° C. to about 250° C., depending upon anumber of factors including the length of the carbon chain. At leastpartially fluorinated solvents are preferred, particularly thosefluorocarbon solvents having at least about 20% by weight fluorine atomsper molecule. Solvents exhibiting surface energies of 18 dynes/cm orlower are preferred, with solvents having surface energies of 13dynes/cm or lower being more preferred and those having 9 dynes/cm beingeven more preferred. In preferred embodiments of the methods of thepresent invention, the solvent is substantially recovered after acoating procedure. Volatile fluorinated surfactants may be included inthe coating formulations of the present invention.

[0087] Additives may be incorporated into or polymerized with thecoating polymers and monomers used to provide coatings according to theinvention having improved toughness, chemical resistance, hardness,softness, processability, elasticity, adhesion, color, texture,thickness and/or uv-resistance. Hydrophobic additives are preferred.Chemically resistant additives are preferred. Additives includingnon-trifluoromethyl-containing reactants and/or monomers may be added inamounts ranging from 1 to about 95% by weight and are described in moredetail below.

[0088] According to an embodiment of the present invention, extremelyhydrophobic surfaces on a variety of articles not limited to laboratoryvessels can be formed. The compositions of the present invention areuseful for any article which is intended to be exposed to elements, thatis, exposed to the environment, exposed to precipitation, unprotected,unsheltered. The compositions of the present invention provide surfacesthat are preferably weatherable, rust resistant, corrosion resistant,able to maintain the appearance of a surface, able to withstand contactwith precipitation without degradation, chemically resistant andmechanically resilient. Compositions are provided that combinerelatively soft polymers of unbranched trifluoromethyl-containingmonomers, and tough, chemically resistant non-fluorinated resins such asacrylics, cellulosics, epoxy, polyesters, silicones, urethanes,anhydrides, amines, polyols, vinyls, vinyl ethers, and combinationsthereof. These mixtures may produce surfaces that are rich intrifluoromethyl groups and interior compositions that are substantiallynon-fluorinated.

[0089] The coating compositions for articles not limited to laboratoryvessels, according to the present invention, can include functionalizedfluoropolymers that have cross-linkable chemical groups, for example,Lumiflon® FE3000, FE4100, FE4200, FE4400, LF 100, LF200, LF302, LF400,LF600X, LF710N, LF800, LF910LM, and LF916N, from Asahi Glass Co., Tokyo,Japan. The coating compositions of the present invention can includefluorourethanes, for example, those available from Century 2000Coatings, Alexandria, Va. and those disclosed in U.S. Pat. No. 4,132,681to Field, which is herein incorporated in its entirety by reference.Particularly preferred are fluorourethanes comprising polymers ofpolyisocyanates and fluorine-containing diols, resulting in goodchemical and mechanical properties. These fully or partially fluorinatedresins may be used as primers for other coatings of the presentinvention or as mixtures with polymers and/or monomers according to thepresent invention.

[0090] The coating formulations for articles can produce extremelyhydrophobic substantially unbranched highly populated trifluoromethylsurfaces and interior compositions that are unfluorinated, partiallyfluorinated or perfluorinated. The phrase “highly populated” applies tosurface populations of 15% by area or greater trifluoromethyl groups.

[0091] The coating compositions for articles not limited to laboratoryvessels, of the present invention, can comprise: a copolymer of at leastone fluorine-containing monomer; a perfluoropolymer;tetrafluoroethylene; perfluoro-2,2-dimethyl-1,3-dioxole (PDD);fluoroethylene-propylene; a polymer containing difluoromethylene; afunctionalized fluoropolymer; the polymerization product of a branchedtrifluoromethyl (TFM) containing monomer; or combinations thereof.

[0092] According to some embodiments of the present invention, thecoating composition for articles includes an aromatic or aliphaticpolyurethane. According to some embodiments of the present invention,the coating preferably comprises the polymerization product of anisocyanate-containing monomer. Optionally, the coating can furthercomprise a cellulosic; a polyester; the polymerization product of anunsaturated monomer; a condensation polymer; a silicone polymer; anepoxy; or combinations thereof.

[0093] The present invention also provides a coated formed rough surfacefor articles not limited to laboratory vessels. The coating comprises atleast one fluorinated component including a fluorinated monomer or apolymerization product thereof. The fluorinated monomer has from about 3to about 40 fluorine atoms and at least one trifluoromethyl group. Theformed rough surface has features smaller than about 100 microns. Thecoated surface provides a surface area populated with 30% by area ormore trifluoromethyl groups and a surface energy of about 22 dynes/cm orlower. The formed rough surface can comprise a pattern of features.

[0094] According to some embodiments of the invention, hydrophobiccoatings are made of a polymerization product of a fluorinated monomerhaving a terminal trifluoromethyl group, and further containing smallamounts of co-monomers, for example, silanes, that serve to promoteadhesion to metal, glass or ceramic vessels without compromising theextremely low surface energy of the coating. Coupling agents may also beused as adhesion promoting monomers and include those listed in Table 1under the heading “Coupling Agents” in the Polymer Encyclopedia.Exemplary coupling agents include vinyltrimethoxysilane,chloropropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and3-methacryloxypropyl-trimethoxysilane. Such silanes and coupling agents,if present, can be present in amounts of from 1% by weight to 10% byweight, more preferably from about 2% by weight to about 5% by weight.If co-monomer is added, the amount added is not so much as to cause thesurface population of trifluoromethyl groups to be less than 30% byarea.

[0095] Other adhesion promoting monomers can be added to the coatingformulations of the invention. If used, adhesion promoting monomersother than silanes are preferably added in amounts of from about 1% byweight to about 40% by weight, more preferably from about 5% by weightto about 20% by weight, based on the weight of the polymerizationproduct making up the coating material. Adhesion promoting monomerswhich may be used include alkoxy terminated monomers and methacrylateesters and acrylate esters listed as adhesion promoting monomers on page16 of the 1994 Sartomer Product Catalog, including mono-, di- andtrifunctional acrylate or methacrylate ester monomers.

[0096] Other additives which may be incorporated or polymerized with theterminal trifluoromethyl-containing monomers or products of theinventive coatings include high glass transition temperature (highT_(g)) perfluorinated or non-perfluorinated monomers, and low T_(g)perfluorinated or non-perfluorinated monomers. High T_(g) monomers canbe included to form hard hydrophobic coatings for laboratory vessels,which are highly resistant to solvent removal and retention ofbiological sample. Preferably, the coating composition comprises afluoropolymer having a T_(g) of greater than 100° C., more preferably,greater than 140° C. The hard coatings are harder than similar coatingswhich differ only in that they do not incorporate the high T_(g)component. High T_(g) monomers which may be employed include thosefluorochemical acrylate or methacrylate monomers which form homopolymersexhibiting T_(g)'s of 50° C. or higher. Exemplary additives of thiscategory are available from the 3M Company as FX-14 (homopolymerT_(g)=60° C.), L-9187 (homopolymer T_(g)=60° C.), and L-11913(homopolymer T_(g)=116° C.). Of the exemplary monomers denoted above,L-11913 is a preferred monomer, and has the formula:cyclo-C₆F₁₁CH₂OCOC(CH₃)═CH₂. If L-11913 is incorporated, it ispreferably employed in an amount of from about 1% by weight to about 60%by weight, based on the weight of the coating.

[0097] Low T_(g) monomers can be included to form soft, hydrophobiccoatings for laboratory vessels, which are highly resistant to solventremoval and retention of biological sample. The soft coatings are softerthan similar coatings which differ only in that they do not incorporatethe low T_(g) component. Low T_(g) additive monomers can be used to formhydrophobic pressure sensitive adhesive coatings, which find many usesincluding the ability to adhere to covering materials such as Teflontape or high T_(g) coatings of the present invention, even underwater.Low T_(g) monomers which may be employed include fluorochemical acrylateor methacrylate monomers which form homopolymers having T_(g)'s of about5° C. or lower, preferably about 0° C. or lower. More preferred lowT_(g) monomers have terminal trifluoromethyl groups. Exemplary additivesof this category are available from the 3M Company as FX-189(homopolymer T_(g)=3° C.), L-9186 (homopolymer T_(g)=0° C.), L-9911(homopolymer T_(g)=—53° C.), L-12044 (homopolymer T_(g)=—23° C.),L-12043 (homopolymer T_(g)=—5° C.), and L-9367 (homopolymer T_(g)=—120°C.). Of the foregoing monomers, L-9186 is a preferred monomer and hasthe formula: C₇F₁₅CH₂OCOCH═CH₂. Combinations of different low T_(g) andhigh T_(g) monomers may be added to the coating formulations of thepresent invention to provide the coating with a specific hardness orpressure sensitive adhesiveness.

[0098] Other additives which may be added to the coating solutions ofthe invention include perfluorinated and non-perfluorinatedplasticizers. Plasticizers can be added in amounts of from about 1% byweight to about 30% by weight, more preferably 5% by weight to about 10%by weight, based on the weight of the coating. Exemplary plasticizersinclude high boiling point Fluorinert solvents from the 3M Companyincluding FC-71, and high boiling point perfluorinated polyethersavailable from Ausimont USA, Inc., including HT 270.

[0099] Cross-linkable monomers may be incorporated into the coatingsolutions, suspensions and formulations according to embodiments of thepresent invention. Cross-linkable monomers may preferably be used forsome applications in amounts ranging from about 1% by weight to about95% by weight, preferably from about 5% by weight to about 70% byweight, and even more preferably from about 10% by weight to about 20%by weight. Cross-linkable monomers which may be incorporated includeepoxies such as novolac epoxies, bisphenol A epoxies, acrylates,silicones, urethanes, anhydrides, and silicates.

[0100] Reactive non-fluorinated monomers and resins can also be added tothe coating formulations of the invention to provide differentproperties to the coatings. According to embodiments of the invention,reactive monomers and resins such as methacrylate monomers, siliconemonomers, epoxy monomers, urethane monomers and oximes can be includedin the coating formulations.

[0101] According to embodiments of the invention, coating formulationsare provided comprising epoxy monomer or resin in amounts of from about20% by weight to about 95% by weight, based on the total weight of thecoating formulation. Preferably, from about 30% by weight to about 70%by weight epoxy monomer may be included in a curable coatingformulation. Epoxy resins may be used including the EPON Resins fromShell Chemical Company, Houston, Tex. for example, EPON Resins 1001 F,1002F, 1007F and 1009F, as well as the 2000 series powdered EPON Resins,for example, EPON Resins 2002, 2003, 2004 and 2005. Preferably, theepoxy monomer or resin has a high crosslink density, a functionality ofabout 3 or greater, and an epoxy equivalent weight of less than 250.Exemplary epoxies which may be employed according to embodiments of theinvention include The Dow Chemical Company (Midland, Mich.) epoxynovolac resins D.E.N. 431, D.E.N. 438 and D.E.N. 439.

[0102] If an epoxy is included in the coating formulation, a curingagent for the epoxy may be added in amounts of from about 1% by weightto about 10% by weight of the epoxy component. The curing agent may be acatalyst or a reactant, for example, the reactant dicyandiamide. Fromabout 1% by weight to about 50% by weight epoxy solvent, based on theweight of the coating formulation, may also be included in the coatingformulations. Epoxy solvents can be added to liquify the epoxy monomeror resin or adjust the viscosity thereof. Preferred epoxy solvents aretriethylphosphate and ethylene glycol. A separate epoxy solvent may notbe needed according to some embodiments of the invention wherein theepoxy is liquid at room temperature or wherein a fluorinated monomer orsurfactant component of the coating formulation acts as a solvent forthe epoxy.

[0103] Even when a large amount of non-fluorinated epoxy is included ina coating formulation according to the invention, surface populations oftrifluoromethyl groups of about 30% by area or more can nonetheless beachieved on the coating. Prepolymerized trifluoromethyl-containingmonomers and/or reactive trifluoromethyl -containing monomers in thecoating formulation tend to migrate to the surface of the coating duringheat curing of the epoxy. The trifluoromethyl-containing components aremobile during epoxy curing due to thermal forces, convective forces,evaporative forces and diffusion forces. If included in a formulation,volatile trifluoromethyl-containing monomer is mostly driven off duringheat curing of the epoxy, but can be polymerized into the coating in thepresence of peroxide or azo compound catalysts, initiators or promoters.

[0104] According to some embodiments of the invention, the coatingformulation comprises an aqueous suspension of thetrifluoromethyl-containing component such as ZONYL NWA, from DuPont.Suspension formulations according to the invention, may further includeadditives as discussed above, including epoxy resins. Exemplarywaterborne epoxy resins which may be used in aqueous suspension coatingformulations according to the invention include the EPI-REZ Resins fromShell Chemical Company, for example, the EPI-REZ Resins WD-510, WD-511,WD-512, 3510-W-60,3515-W-60,3519-W-50,3520-WY-55 and 3522-W-60. Thecoating composition may comprise microparticles, microfibers, foamingand/or pore-forming agents, and may be dried, cured, and/or hardened soas to produce sufficient surface roughness to provide high contactangles to water.

[0105] According to some embodiments of the invention, a coatingsolution or suspension is provided which comprises prepolymerizedfluorinated monomer, reactive non-polymerized fluorinated monomer, andan additional additive, for example, at least one of the additivesdiscussed above. The additional additive may be added in substantialamounts, for example, up to 95% by weight, provided the resultantcoating has a surface population of trifluoromethyl groups which isabout 30% by area or more. Preferably, coating techniques which involveapplication of a solution containing unreacted monomer further include astep of recovering unreacted monomer after coating.

[0106] According to some embodiments of the invention, an operationalsurface of a laboratory vessel is at least partially coated withtrifluoromethyl-containing monomers and non-trifluoromethyl-containingmonomers followed by polymerization of the monomers and removal andrecovery of unreacted monomers. According to some embodiments, themonomers are applied from a coating solution which further includes afluorinated solvent. Preferably, when reactive fluorinated monomers areused to coat an operational surface, and subsequently polymerized,unreacted monomer is removed and substantially recovered after coatingand curing.

[0107] According to some embodiments of the invention, the coatingsolution comprises the polymerization product of substantially terminaltrifluoromethyl-containing monomers, and unreacted terminaltrifluoromethyl-containing monomers. After coating an operationalsurface, the coating is then subsequently polymerized to form polymerfrom the unreacted monomer in the coating solution. Such a procedureresults in extremely hydrophobic coatings. When partially unreactedcoating solutions are used, they may also include from about 15% byweight to about 95% by weight, based on the weight of the coating, ofnon-perfluorinated functional monomer, such as an epoxy.

[0108] Linkage mechanisms for binding the trifluoromethyl-containingmonomer or polymer of the present coating formulations to an operationalsurface of a vessel include functional linkage groups such as peroxidecatalyzed linkages, azo catalyzed linkages, free radical inducedlinkages, cationically induced linkages, radiation induced linkages,vinyl linkages, methacrylate linkages, urethane linkages, epoxylinkages, condensation linkages, silane linkages, and siloxane linkages.

[0109] According to embodiments of the invention, prepolymerizedhydrophobic coatings according to the invention comprise apolymerization product of a substantially trifluoromethyl-containingmonomer, that is, having at least about 15%, preferably 30%, of theterminal groups of the reactant monomer or monomers comprisingtrifluoromethyl groups, and from about 1% by weight to about 10% byweight of additional comonomers. The additional comonomers havingfunctionality that is polymerizable by a second, different mechanismthan the mechanism used to polymerize the substantiallytrifluoromethyl-containing monomer. The second polymerization mechanismmay be activated during or following application of the hydrophobiccoating to an operational surface, allowing the hydrophobic coating tobecome crosslinked with itself or with the vessel walls. For example,the initial polymerization may be carried out as an addition reaction ofacrylates or methacrylates using a free radical catalyst, whereas thesecond polymerization may be carried out as a cationic reaction ofepoxides using a cationic or acid catalyst. An exemplary material havingepoxy functionality and acrylate functionality is glycidyl-methacrylate.Peroxides will attach hydrocarbon groups to hydrocarbons on the surfaceof the vessel.

[0110] According to some embodiments of the invention, low surfaceenergies can be obtained when a terminal trifluoromethyl-containingmonomer is coated onto the operational surface of a vessel andsubsequently polymerized after coating. Substantially non-branchedfluoroalkyl and perfluoroalkyl ethylenically unsaturated monomers arepreferred according to embodiments of the invention.

[0111] According to some embodiments, a methacrylate group is used asthe preferred ethylenically unsaturated monomer. Other monomers whichcan be used include fluorinated or perfluorinated silicones, epoxies,urethanes and oximes. Polymers made from mixtures of acrylates,urethanes and epoxies are particularly preferred. According to someembodiments, both prepolymerized fluorinated monomer and reactivenon-polymerized fluorinated monomer are used in the coating formulation,and after application to an operational surface, the reactive monomer isthen polymerized or volatilized. Preferably, the reactive monomer ispolymerized.

[0112] Another method of forming a coating according to embodiments ofthe invention is by using monomers capable of free radical linkages.Such monomers can be attached to vessel surfaces if the vessel surfacesare first treated by ionizing radiation or other means to generate freeradicals across the surface. A monomer capable of free radical linkagescan be formed by mixing a fluoroalkyl ethylenically unsaturated monomerdissolved in a suitable fluorocarbon solvent with an effective amount ofa free radical initiator. Vessels coated with the mixture are thenheated to the temperature at which the free radical initiator initiatesfree radical generation. Many conventional azo compounds have anappropriate activation temperature, particularly within the range of30-200° C. Many azo compounds may be used which are activated by visibleor ultraviolet light.

[0113] According to some embodiments of the invention, when working withliquids which only slightly wet fluorinated surfaces, for example, whenthe contact angle between the liquid and the surface is greater than90°, it may be desirable to provide a rough surface coating on alaboratory vessel to more effectively prevent runoff of the liquid asmight occur from a smooth hydrophobic coating. Such would be theobjective when it is desired to maintain a drop of liquid sample on amicroscope slide. A microscopically roughened or porous hydrophobicsurface which will not be wetted can be made according to the presentinvention by adding microscopic particles of a surface roughening agent,for example, a micropowder, to the hydrophobic coating material or tothe surface to which the coating polymer is to be applied. According toembodiments of the invention, microscopic particles can be added tocoating formulations of the present invention which comprise (1) apolymerization product of a trifluoromethyl-containing monomer, (2) anunreacted trifluoromethyl-containing monomer, or both (1) and (2).Microscopic particles can also be added to coating formulations whichfurther include a fluorinated solvent.

[0114] While many microparticles may be used as surface rougheningagents according to the present invention, micropowders are a preferredclass of surface roughening agents. Micropowders are defined herein asthose powders or particles having average diameters of from submicronsizes up to 100 microns. A preferred micropowder average diameter isabout 10 microns or less. Hydrophobic materials are particularlypreferred for the micropowders. Suitable micropowders include siliconglass particles with and without silane coatings, pigments, Teflongpowders, flour, cornstarch, siliconized glass, fluorosiliconizedinorganic pigments, and micronized cellulosics. According to embodimentsof the invention, a composite surface is formed by adding asubstantially uniformly sized micropowder to a fluoropolymer or afluoromonomer which is to be subsequently coated and then polymerized.The use of micropowders exhibiting wide particle size distributions alsoprovides preferred coatings according to some embodiments of the presentinvention.

[0115] Inert micropowders are preferred, particularly for applicationswhere the resultant coating is exposed to liquids which are other thanaqueous in nature. One particularly preferred micropowder is asiliconized glass particulate material having a 0.3 micron averageparticle size diameter available as TULLANOX HM 250 or TULLANOX HM 250D,from Tulco, Inc., Ayer, Mass. Another preferred micropowder is Teflon®MP 1200, available from DuPont Polymer Products Department, Wilmington,Del. and having an average particle diameter of about 4 μm.

[0116] Microfibers are another class of surface roughening agents andmay be used in the coating compositions of the present invention. Inertmicrofibers are preferred according to some embodiments of theinvention, for example, some embodiments requiring mechanical strength.A preferred microfiber is a cellulose microfiber having an averagediameter of about 4 microns and an average length of about 40 microns,for example, TECHNOCELL 40™ available from EastTec, of Pennsylvania.Microfibers of longer lengths are also preferred.

[0117] The methods of the present invention may comprise diluting atrifluoromethyl-containing coating polymer solution or suspension priorto applying the solution or suspension to an operational surface of alaboratory vessel. The coating solution or suspension is preferablydiluted to between about 0.01 and 2 percent by weight coating polymer.Higher weight percentages of the polymer may be used although higherconcentrations tend to clog small orifices such as the opening at theend of a pipette tip for a volumetric pipettor, or small orifices suchas nozzles and nozzle openings in inkjet printer print heads.

[0118] One preferred method for applying a coating polymer solution orsuspension comprises dip-coating a laboratory vessel or other articlesinto a polymer solution or suspension. Other coating methods may also beused, including spray coating, tumbling in solution, brush coating,padding, spraying, fogging, transferring, painting, printing,stenciling, screen printing, pad printing, ink jet printing, injectionmolding, laminating and doctoring. For articles having interior wallsdefining a reservoir portion, the area of the article around anddefining an opening to the reservoir is preferably also coated. Forsimultaneously coating a large number of small articles, each having areservoir portion, a tumbling method of coating is preferred.

[0119] Dip coating may be used according to some embodiments of theinvention to apply the coating polymer from a solution of the polymerdissolved in a fluorosolvent or from a suspension of the polymer. Aftercoating the polymer solution, the coating is allowed to dry and solventor carrier is driven off.

[0120] After forming a first coating of polymer according to theinvention, the methods of the invention may also comprise applying atleast one other coating formulation comprising a polymer having terminaltrifluoromethyl groups. According to some embodiments of the invention,one or more coatings of the same or different terminaltrifluoromethyl-containing polymers may be applied, depending upon thedesired surface energy properties of an operational surface beingcoated.

[0121] According to some embodiments of the invention, the coatingformulation is not a polymer solution or suspension but insteadcomprises a fluidized micropowder of the polymerization product ofentirely or substantially trifluoromethyl-containing monomers. Themicropowder formulation can be applied to at least a portion of anarticle surface, for example, an operational surface of a laboratoryvessel, and melted to form a hydrophobic coating having an extremely lowsurface energy, a high resistance to solvent removal, and for laboratoryvessels, a low retention of biological samples. According to someembodiments, the coating formulation comprises a fluidized micropowderof the polymerization product of entirely or substantiallytrifluoromethyl-containing monomers, and at least one substantiallynon-perfluorinated resin. The micropowder and resin are applied to asurface, for example, an operational surface of a laboratory vessel andheated to melt the fluidized micropowder.

[0122] According to embodiments of the invention, the coating polymer orcoating monomer formulation of the invention is applied as a micropowderalong with at least one of a curable resin and a non-curable resin.Preferably, the at least one resin is substantially non-perfluorinated.Curable resins which can be used in formulations of micropowder coatingmaterial include epoxy resins, urethane resins, acrylate resins,methacrylate resins. Highly cross-linked resins provide excellentsolvent resistance according to embodiments of the invention. Anexemplary resin having a high crosslink density is the epoxy novolacresin D.E.N. 439, available from Dow Chemical Co., Midland, Mich.

[0123] According to other embodiments, resins with low cross-linkdensities may be employed for coatings subsequently used with aqueousmediums. An exemplary low crosslink density resin is the fusion solidEPON Resin 1004F available from Shell Chemical Company, Houston, Tex.EPON Resin 1004F is a bisphenol A epoxy resin having a melting point ofabout 100° C. Other EPON Resins from Shell Chemical Company may also beused, including 1001F,1002F,1007F and 1009F, as well as the 2000 seriespowdered EPON Resins, for example, EPON Resins 2002, 2003,2004 and 2005.

[0124] Non-curable resins which may be employed include powdered ethylcellulose, powdered polyethylene, powdered polypropylene and powderedpolyvinylidenedifluoride. Cellulose acetate butyrate pellets also be jetmilled and applied as a powder. Cellulose acetate butyrate is typicallynon-curable but can be cross-linked with peroxides.

[0125] The substantially non-perfluorinated resin is preferablynon-fluorinated according to some embodiments of the invention.

[0126] The micropowders and resins used according to embodiments of theinvention can be formed, for example, by jet milling. The micropowdersand resins are preferably particles having an average diameter of about50 microns or less, with average diameters of 10 microns or less beingmore preferred. The powders can be electrostatically sprayed onto asurface with or without a curing agent.

[0127] Micropowders according to the present invention may also beprepared as latexes in aqueous suspensions, subsequently separated fromthe liquid phase, and dried. Nanopowders and micropowders withsubstantially trifluoromethyl surfaces may be prepared in radiofrequency and microwave plasmas of trifluoromethyl-containing gases.

[0128] In another embodiment of the invention, the coating is formedfrom a fluidized micropowder product of trifluoromethyl-containingmonomer and substantially non-perfluorinated resin, wherein themicropowder is applied and melted on an operational surface.

[0129] In another embodiment of the invention, a fluidized micropowderof a non-perfluorinated resin is coated with the polymerization productof a substantially trifluoromethyl-containing monomer. The powder issubsequently melted to form a hydrophobic coating.

[0130] In another embodiment of the invention, a surface is coated witha coating formulation comprising a fluidized micropowder of apolymerization product of substantially trifluoromethyl-containingmonomer, and a hydrophobic non-melting micropowder that does not melt attemperatures required for formation of the coating. The formulation isthen heated or sintered to melt the fluidized polymerization productmicropowder without melting the non-melting micropowder. The non-meltingmicropowder is preferably selected from the group consisting of Teflonmicropowders, Tefzel™ micropowders, Kynar™ micropowders, polyvinylidenedifluoride micropowders, and polypropylene micropowders.

[0131] According to embodiments of the invention which involve formingcoatings by melting micropowders, the coating formulations may beapplied as a suspension to the operational surface and subsequentlydried prior to melting.

[0132] Another method of forming laboratory vessels having hydrophobiccoatings according to the present invention involves preinjecting orcoinjecting a coating formulation prior to or during the laminar flow ofmolten materials injected into a mold or through an orifice to formarticles, for example, laboratory vessels. The coating formulationcomprises the prepolymerization product of a trifluoromethyl-containingmonomer, preferably a product which has from about 50% to 100% ofexposed terminal groups being trifluoromethyl groups. The preinjected orcoinjected coating formulation may also comprise a thermoplastic resinand/or a thermosetting resin. The injectable coating formulation maycomprise mixtures of trifluoromethyl-containing monomer, catalyst, andresin. The injectable coating formulation may comprise mixtures ofmolten prepolymerized trifluoromethyl-containing monomer andmicroparticles, to form coatings exhibiting extraordinarily high contactangles of 160° or more to aqueous liquids. The injectable coatingformulations may comprise mixtures of molten prepolymerized entirely oressentially trifluoromethyl-containing monomers, other resins, andmicroparticles, which are preinjected or coinjected to or during thelaminar flow of molten materials injected into a mold or through anorifice to form coatings on the resultant vessels having extraordinarilyhigh contact angles to aqueous liquids, high resistance to solventremoval, and low retention of biological samples.

[0133] According to yet other embodiments of the invention, a tubularlaboratory vessel such as a microcentrifuge tube or test tube isprovided and comprises a tubular body having an interior sidewall and aclosed lower end having an interior surface. A hydrophobic coatingaccording to the invention is applied to the interior sidewall but notto the interior surface of the closed lower end, or the interior closedend is substantially free of the coating. An aqueous sample placed inthe tubular body tends to be retained at the closed lower end of thevessel and tends not to creep or advance onto the coated interiorsidewall, even during movement of the vessel.

[0134] Other applications of the coating compositions of the presentinvention include their use on ink-jet ink print heads to formhydrophobic surfaces surrounding ink jet nozzle orifices. Hydrophobicproperties in such regions of an inkjet print head are particularlybeneficial in the use of organic solvent based inkjet inks which haveeven a greater tendency to wet-out on the print head than do aqueousbased ink jet inks. The hydrophobic nature of such a print head designprevents nozzle clogging and cross-contamination between individualorifices of the print head. The entire print head surface containing theink jet nozzle orifices can be coated with the hydrophobic coatingcomposition of the present invention or only in areas surrounding theindividual orifices. The compositions for such uses can may or may notcontain a hardenable material along with the trifluoromethyl-containingcomponent.

[0135] The present invention is exemplified with reference to thefollowing Examples. In the Examples below, the surface energies of thecoatings was determined as follows. A series of hydrocarbon oils withknown surface tensions were used to develop a graph of liquid surfacetensions verse the cosines of the liquid contact angles for each oil.The interpolated intercept of the graphed line at a cosine of oneindicates the surface energy of the coating.

EXAMPLE 1

[0136] A plurality of polypropylene pipette tips were enclosed in amonofilament polyester mesh bag and the bag was placed in a tumbling oragitating device. The mesh bag permitted treatment of the pipette tipsby allowing coating solution to pass through the bag and substantiallywet the surfaces of the pipette tip, including surfaces at and aroundthe tip openings. The tumbling device was fitted with special gaskets torender the machine interior air-tight and fluid-tight. To the machineinterior was also added a sufficient amount of coating solution to atleast partially immerse the bag of pipette tips. The coating solutioncomprised a diluted solution of a fluorocarbon polymer having terminaltrifluoromethyl groups. The fluorocarbon polymer solution is availableas FluoroPel from Cytonix Corporation. The FluoroPel solution providesthe polymer completely dissolved in a fully fluorinated solvent ofperfluorinated fluorocarbons having an average carbon chain length offrom about 7 to about 8 carbon atoms. The solvent exhibited a boilingpoint of from about 90° C. to about 100° C. Additional perfluorinatedsolvent or similar perfluorinated fluorocarbon solvent was added as adiluent to the FluoroPel solution to provide a coating solution having asolids content of coating polymer of about 0.5% by weight.

[0137] The tumbling device was equipped with a blower for removingvolatile solvent from the coating and interior airspace, and with aheater for heating air to be blown by the blower. The tumbling devicewas run to agitate and tumble the pipette tips and the coating solution,thus evenly distributing the coating solution on the surfaces of thetips and sufficiently wetting the surfaces of the tips, includingsurfaces at or around the tip openings. The interior of the device wasmaintained at or below room temperature during solution coating of thetips. After a few minutes of tumbling, a drain in the interior of thedevice was opened to allow excess coating solution to drain out from thetumbling device interior during further tumbling. After a few minutes ofdraining with continued tumbling, the blower and heater were turned onand air having a temperature of about 80□C. was blown through the deviceinterior, and exhausted. The heated air evaporated solvent from thecoated solution and from the interior airspace of the tumbling device.The bag of pipette tips continued to tumble during the drying process.The drained and evaporated solution and solvent was collected,reconcentrated and recycled. The coating polymer was not volatile underexposure to the 80° C. air.

[0138] The coated and dried pipette tips were removed from the deviceinterior and mesh bag. Both exterior and interior surfaces of the tipswere coated by the process. The coated surfaces had a resultant surfaceenergy of less than about 10 dynes/cm and an estimated surfacepopulation of trifluoromethyl groups of about 50% by area or more.

EXAMPLE 2

[0139] A highly chemically and solvent resistant hydrophobic coating fora microscope slide was prepared. The coating was provided from a coatingformulation having the following ingredients:

[0140] 50 parts by weight high functionality novolac epoxy resin,available as D.E.N. 439 from The Dow Chemical Company, Midland, Mich.having an epoxy functionality of 3.9, an epoxy equivalent weight ofabout 220, and a high cross-link density;

[0141] 8% by weight dicyandiamide as a reactant agent for curing theepoxy, based on the weight of the epoxy;

[0142] 50 parts by weight calcinated pigment;

[0143] 10 parts by weight epoxy solvent triethylphosphate to liquify andreduce the viscosity of the epoxy;

[0144] 10 parts by weight trifluoromethyl-containing polymer, comprisingPerFluoroCoat (PFC) 468MP (a solution of polymerized and non-polymerizedperfluoroalkyl monomers) available from Cytonix Corporation; and

[0145] 1 part by weight 3 -glycidoxypropyltrimethoxysilane.

[0146] The coating formulation was mixed, screen printed on a microscopeslide, heat cured and allowed to dry. The resultant cured and driedcoating exhibited a contact angle to water of 120°, was very hard, couldnot be scratched with a#8H pencil, and was chemically resistant toremoval in a plurality of common lab solvents including acetone, water,chloroform, trichloroethane and trifluoroethane, at 20° C. The coatingexhibited a very low surface energy, and the population oftrifluoromethyl groups on the exposed surface of the coating exceeded80% by area as determined by surface energy analysis.

EXAMPLE 3

[0147] A composite hydrophobic coating was prepared and provides a roughsurface upon curing. The coating can exhibit extremely high contactangles to water. The coating was prepared as follows:

[0148] 50 parts by weight D.E.N. 438 epoxy, 70 parts by weighttriethylphosphate, 4 parts by weight dicyandiamide, and 1 part by weight3-glycidoxypropyltrimethoxysilane were thoroughly mixed together. Then,50 parts by weight TiO₂ having an average particle size diameter ofabout 1 μm was added and the mixture was again mixed thoroughly. Then,100 parts by weight Teflon® MP 1200 powder was added and the mixture wasagain mixed thoroughly. Then, 100 parts by weight Teflon® MP 1200 powderwas added and the mixture was again mixed thoroughly. Then, 10 parts byweight PFC 468MP was added and the mixture was again mixed thoroughly.The resulting formulation was applied to an operational surface of alaboratory vessel and allowed to cure for 3 minutes at 200° C.

EXAMPLE 4

[0149] A composite hydrophobic coating was prepared and provides a roughsurface upon curing. The coating can exhibit extremely high contactangles to water. The coating was prepared as follows:

[0150] 90 parts by weight Shell 1004-QX-55 (bis-A epoxy in xylene andpropylene glycol monomethyl ether acetate), 1 part by weight imidizol(optional), 40 parts by weight ethylene glycol, and 10 parts by weightorganic pigment were thoroughly mixed together. Then, 10 parts by weightTullanox glass micropowder was added and the mixture was again mixedthoroughly. Then, 10 parts by weight PFC 468TF (solution ofperfluoroalkyl polymer in Freon TF), available from Cytonix Corporation,was added and the mixture was again mixed thoroughly. The resultingformulation was applied to an operational surface of a laboratory vesseland allowed to dry at room temperature for 24 hours.

EXAMPLE 5

[0151] A highly chemical and solvent resistant hydrophobic coating forspraying or dipping was prepared. The coating was provided from acoating formulation having the following ingredients: Part A 5 partsFuturathane 660 part A (Futura Coatings, Inc.-USA) 5 parts acetophenone(Aldrich Chemical) 20 parts Vertrel MCA Part B 33 parts Vertrel MCA(Dupont) 10 parts Asakalin 225 (Asahi Glass) 0.5 part 9187 polymer(Cytonix) 1.5 parts 9187 monomer (3M) 15 parts Futurathane 660 part B(Futura Coatings, Inc.-USA)

[0152] Parts A and B were mixed and sprayed onto glass, plastic andmetal articles and allowed to and cure under ambient conditions for 72hours. The resultant coatings were scratch resistant to a #6 pencil, hada contact angle to water of 120°, and were not altered by acetone,toluene or chloroethane. The population of trifluoromethyl groups at thesurface exceeded 80 percent

EXAMPLE 6

[0153] A highly chemical and solvent resistant hydrophobic coating forspraying or dipping was prepared. The coating was provided from acoating formulation having the following ingredients: Part A 5 partsFuturathane 660 part A (Futura Coatings, Inc.-USA) 5 parts acetophenone(Aldrich Chemical) 20 parts Vertrel MCA 24 parts Zonyl 1300 micropowder(Dupont) Part B 33 parts Vertrel MCA (Dupont) 10 parts Asakalin 225(Asahi Glass) 0.5 parts 9187 polymer (Cytonix) 1.5 parts 9187 monomer(3M) 15 parts Futurathane 660 part B (Futura Coatings, Inc.-USA)

[0154] Parts A and B were mixed and sprayed onto glass, plastic andmetal articles and allowed to dry and cure under ambient conditions for72 hours. The resultant coatings had a contact angle to water of 150°,and were not altered by acetone, toluene or chloroethane. The populationof trifluoromethyl groups at the surface exceeded 80 percent.

EXAMPLE 7

[0155] A highly hydrophobic coating composition for spraying or dippingwas prepared. A coating was provided from the coating formulation whichhad the following ingredients: 100 parts Asakalin 225 (Asahi Glass)  5parts 9187 polymer (Cytonix)  25 parts 9187 monomer (3M) 100 partsHelmsMan Spar Urethane (Minwax, Upper Saddle River, NJ)

[0156] Ingredients were mixed and sprayed onto glass, plastic and metalarticles and allowed to dry and cure under ambient conditions for 24hours. The resultant coatings were scratch resistant to a #2 pencil andhad a contact angle to water of 120°.

EXAMPLE 8

[0157] A highly hydrophobic coating for spraying or dipping was preparedthe coating was provided from a coating formulation having the followingingredients: 200 parts Asakalin 225 (Asahi Glass)  5 parts 9187 polymer(Cytonix)  25 parts 9187 monomer (3M) 120 parts Zonyl 1300 micropowder100 parts HelmsMan Spar Urethane (Minwax, Upper Saddle River, NJ)

[0158] Ingredients were mixed and sprayed onto glass, plastic and metalarticles and allowed to dry and cure under ambient conditions for 24hours. The resultant coatings had a contact angle to water of 150°.

EXAMPLE 9

[0159] A highly hydrophobic coating for spraying or dipping wasprepared. The coating was provided from a coating formulation having thefollowing ingredients: 200 parts Asakalin 225 (Asahi Glass)  5 parts9187 polymer (Cytonix)  25 parts 9187 monomer (3M)  80 parts TechnoCel ®40 (available from Cellulose Filler Factory, Chestertown, MD) 100 partsHelmsMan Spar Urethane (available from Minwax, Upper Saddle River, NJ)

[0160] The ingredients were mixed and sprayed onto glass, plastic andmetal articles and allowed to dry and cure under ambient conditions for24 hours. The resultant coatings had a contact angle to water of 150°.

EXAMPLE 10

[0161] A highly hydrophobic coating for printing or painting wasprepared. The coating was provided from a coating formulation having thefollowing ingredients:

[0162] 100 parts by weight N68 from Norland

[0163] 10 parts by weight Asakalin 225 from Asahi Glass

[0164] 10 parts by weight Zonyl TA-N from DuPont

[0165] The ingredients were mixed and painted onto glass, plastic andmetal articles and cured in mid-day summer sunlight in Virginia for onehour. The resulting coatings had a contact angle to water of 120°. Thesurface area population of trifluoromethyl groups exceeded 70%.

EXAMPLE 11

[0166] A highly hydrophobic coating for spraying or dipping wasprepared. The coating was provided from a coating formulation having aperfluorinated hardenable resin. The coating formulation had thefollowing ingredients:

[0167] 10 parts by weight Teflon AF 1600 from DuPont

[0168] 100 parts by weight FC-40 from 3M

[0169] 1 part by weight L-9187 polymer from Cytonix Corporation

[0170] The ingredients were mixed and heated to 120° C. for two hours.The resultant material was then painted onto glass, PTFE and metalarticles and cured in an oven at 200° C. for one hour. The resultingcoatings had a contact angle to water of 120°. The surface areapopulation of trifluoromethyl groups exceeded 90%. The surface energy ofthe coating was below 9 dynes/cm compared to the surface energy ofarticles coated with Teflon AF alone, which was about 16 dynes/cm. Theproperties of the inventive coating indicate a substantiallyperfluorooctyl surface on the coatings of the present invention.

[0171] Although the present invention has been described in connectionwith preferred embodiments, it will be appreciated by those skilled inthe art that additions, modifications, substitutions and deletions notspecifically described may be made without departing from the spirit andscope of the invention defined in the appended claims.

What is claimed is:
 1. A composition comprising atrifluoromethyl-containing agent, said agent comprising atrifluoromethyl-containing reactant or reaction product thereof andcomprising: (A) a substantially unbranched terminaltrifluoromethyl-containing structural unit; or (B) a combination of (i)a fluorosilane, (ii) a fluorinated acid anhydride or fluoroanhydride,and (iii) a fluorinated solvent, said composition capable of providing acoating having an exposed coating surface area populated with at leastabout 30% by area trifluoromethyl groups and a surface energy of about22 dynes/cm or lower at 20° C.
 2. The composition of claim 1, whereinsaid agent comprises (B) and said fluorosilane comprises a fluoroalkylalkoxysilane.
 3. The composition of claim 1, wherein said agentcomprises (B) and said fluorinated acid anhydride or fluoroanhydridecomprises trifluoroacetic acid anhydride, trifluorobutyric acidanhydride, or combinations thereof.
 4. The composition of claim 1,further comprising a surface roughening agent.
 5. The composition ofclaim 1, wherein the trifluoromethyl-containing agent is a terminaltrifluoromethyl-containing agent.
 6. An operational surface coated withthe composition of claim
 1. 7. An operational surface coated with thecomposition of claim 1, wherein the operational surface is porous,rough, pitted, foamed, grooved, cross-hatched, or striated, or haspatterned physical features.
 8. An operational surface coated with thecomposition of claim 4, wherein the operational surface is porous,smooth, rough, pitted, foamed, grooved, cross-hatched, or striated, orhas patterned physical features.
 9. A composition comprising afluorinated reactant having from about 3 to about 20 carbon atoms and atleast one trifluoromethyl group, or a reaction product thereof, saidcoating composition further comprising a second component, said secondcomponent comprising a hardenable material, said composition capable offorming a coating having an exposed coating surface area populated withat least about 15% by area trifluoromethyl groups and a surface energyof about 22 dynes/cm or lower at 20° C.
 10. The composition of claim 9,wherein said second component comprises a non-fluorinated hardenableresin.
 11. The composition of claim 9, wherein said second componentcomprises a fluorinated hardenable resin.
 12. The composition of claim9, wherein said second component comprises a perfluorinated hardenableresin.
 13. The composition of claim 9, wherein said coating compositionfurther includes a surface roughening agent.
 14. The composition ofclaim 9, wherein said coating composition further comprises afluorinated solvent.
 15. The composition of claim 9, wherein thefluorinated reactant is a perfluorinated reactant.
 16. An operationalsurface coated with the composition of claim
 9. 17. An operationalsurface coated with the- composition of claim 9, wherein the operationalsurface is porous, rough, pitted, foamed, grooved, cross-hatched, orstriated, or has patterned physical features.
 18. An operational surfacecoated with the composition of claim 13, wherein the operational surfaceis porous, smooth, rough, pitted, foamed, grooved, cross-hatched, orstriated, or has patterned physical features.